The present invention relates to preparations suitable for the prevention and/or treatment of vascular disorders. The invention also relates to the use of these preparations for the prevention and/or treatment of diseases that find their main cause in vascular problems, in particular dementia syndromes.
The vascular system in the human body is well described in the art. An important part of the system are the blood vessels, that generally are divided in arteries and veins, dependent whether they transport blood to or from the heart. They vary in size from large (e.g. the aorta) to very small (capillaries). From an anatomical point of view larger blood vessels in general comprise as observed from the lumen side:    1. the tunica intima, that consists of a smooth (mono) layer of endothelial cells and a subendothelial layer that consists of a loose layer of connective tissue,    2. the tunica media, which consists of a layer of (innervated) smooth muscle cells and elastic fibers, and    3. the tunica adventitia which is composed of loosely woven collagen fibers, which are infiltrated by tiny lymphatic and blood vessels.
The endothelial cells in the tunica intima are in direct contact with blood and have a barrier function for the underlying tissue. This barrier function includes selective transport of components from blood to the underlying tissue and vice versa, and protection of the underlying tissue. Endothelial cells get easily damaged due to a wide variety of causes like mechanic forces or interaction with stressor components such as classic anaphylatoxins, and components that may occur in the blood, such as homocysteine or components that result from treatment with certain types of drugs (e.g. chemotherapeutics). Vascular permeability can further be increased by a wide variety of humoral- and cell-derived mediators.
Endothelial dysfunction can result in a wide range of disorders. Damage to the endothelial layer can disturb the physiological functions thereof such as transport properties and expose the underlying tissue to stressors. Monocytes may migrate to these damaged spots, get caught by adhesion molecules, differentiate into macrophages, which, when activated, may start up an inflammatory reaction. Due to this reaction cytokines may be released, which may trigger the release of reactive oxygen species, or change coagulation behaviour of blood components. This may result in occurrence of plaques in the arteries, which may ultimately result in hypertension, atherosclerosis and (later) arteriosclerosis.
Atherosclerosis may lead to an impaired blood supply to tissue, which may then become ischaemic. This may lead to damage to cells and even apoptose of the cells that depend on the oxygen and nutrient supply via these blood vessels. Tissue that has become ischaemic may thus lose functional capacity.
Dementia syndromes are characterised by an abnormal high and progressive loss of functional capacity of the brain. This process may start relatively early in life, like the dementias that are associated with some forms of epileptics, encephalitis, Huntington's disease, the dementias that can be observed after intoxication by (chronic) alcohol or drug abuse and the dementias due to cerebrovascular accidents and some genetic forms of dementias (early onset dementias). It may also start relatively late in life such as in Alzheimer's disease (presenile dementia), in senile dementia and in atherosclerotic dementia. Dementias may develop suddenly, e.g. after an apoplectic event, or develop very slowly such as in senile dementia.
Alzheimer's disease is characterised by an early step of excision of the amyloid-beta peptide (AB) from the precursor protein (APP) that is present in the endosomes of neurons or other cells of the central nervous system. The AB peptide produced by beta-secretase (BACE) may diffuse outside the cell and polymerize into amyloid filaments, which in turn may develop into mature amyloid plaques, especially when chaperone molecules like protease inhibitors are present. The inflammatory response to the deposits of AB polymers and/or amyloid plaque may eventually lead to neuronal cell death and loss of cerebral function.
Dementia syndromes occur relatively frequently; about 10% of the elderly population in the Netherlands suffer from this disease and still no cure has been found to prevent or treat dementias. Treatment with drugs that increase brain levels of neurotransmitters like acetylcholine, serotonin or (nor) adrenaline are ineffective in the long term and the relatively high doses that often are administered could lead to undesirable side effects.
For the prevention and treatment of vascular disorders no suitable therapy is available either. Vascular disorders and the consequences thereof are a major cause of death in the Western countries. At present vascular disorders are treated by prescribing specific diets that are restricted in cholesterol, saturated fatty acids and in some cases sodium content and by administering drugs that are designed to lower blood pressure (e.g. diuretics), and plasma levels of cholesterol e.g. statins (or other compounds that are able to inhibit the activity of HMG-CoA reductase).
Though some of the treatments are indeed effective in treating part of the phenomena associated with vascular problems, the treatments are not 100% effective in solving the real problem (the cause) and they may demonstrate undesired systemic side effects.